Checking Fuel Pressure
You can tap in a fuel pressure gauge in the line going into the fuel rail from the driver side. Locate the fuse box near drive side mount and look behind it. You should see a metal fuel line connected with a clamp to a fuel hose running to the metal fuel rail on top of the engine.
- Start the car
- Remove fuse number #22 (fuel pump), and wait for the car to choke
- Shut off the car and unplug battery (safety)
- Unscrew the clamp and take out the hose from metal rail near fuse box
- Put the hose into a pressure gauge on one end and use a piece of new fuel hose on another end and clamp it to the metal fuel line
- Make sure everything is tight
- Turn on the ignition in position number one to begin priming the pump at low pressure. Check for leaks
- Attempt to start the car by turning it over for 2-4 seconds at a time. You should check for system leaks between the attempts. The E34 will require about 4-5 attempts before the fuel pressure is up to the specification
- Read the fuel gauge
- 3.5 BAR, +/- .02 BAR
- 50 PSI, +/- 3 PSI
Testing for leaks
After testing the fuel pressure, shut the car off and write down the current fuel pressure. Wait 20 minutes; the pressure should not drop more than 0.5 BAR.
If it does, you have a leak or faulty fuel pump check valve.